APPENDIX G. Radiocarbon-dating Methods and Results

Transcription

1 APPENDIX G Radiocarbon-dating Methods and Results

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3 Consistent Accuracy... Delivered On Time. Beta Analytic Inc SW 74 Court Miami, Florida USA Tel: Fax: Analytical Procedures Mr. Darden Hood Director Mr. Ronald Hatfield Mr. Christopher Patrick Deputy Directors Final Report The final report package includes the final date report, a statement outlining our analytical procedures, a glossary of pretreatment terms, calendar calibration information, billing documents (containing balance/credit information and the number of samples submitted within the yearly discount period), and peripheral items to use with future submittals. The final report includes the individual analysis method, the delivery basis, the material type and the individual pretreatments applied. The final report has been sent by mail and (where available). Pretreatment Pretreatment methods are reported along with each result. All necessary chemical and mechanical pretreatments of the submitted material were applied at the laboratory to isolate the carbon, which may best represent the time event of interest. When interpreting the results, it is important to consider the pretreatments. Some samples cannot be fully pretreated, making their 14 C ages more subjective than samples, which can be fully pretreated. Some materials receive no pretreatments. Please look at the pretreatment indicated for each sample and read the pretreatment glossary to understand the implications. Analysis Materials measured by the radiometric technique were analyzed by synthesizing sample carbon to benzene (92% C), measuring for 14 C content in one of 53 scintillation spectrometers, and then calculating for radiocarbon age. If the Extended Counting Service was used, the 14 C content was measured for a greatly extended period of time. AMS results were derived from reduction of sample carbon to graphite (100 %C), along with standards and backgrounds. The graphite was then detected for 14 C content in one of 9 accelerator-mass-spectrometers (AMS). The Radiocarbon Age and Calendar Calibration The "Conventional 14 C Age (*)" is the result after applying 13 C/ 12 C corrections to the measured age and is the most appropriate radiocarbon age. If an "*" is attached to this date, it means the 13 C/ 12 C was estimated rather than measured (The ratio is an option for radiometric analysis, but included on all AMS analyses.) Ages are reported with the units BP (Before Present). Present is defined as AD 1950 for the purposes of radiocarbon dating. Results for samples containing more 14 C than the modern reference standard are reported as percent modern carbon (pmc). These results indicate the material was respiring carbon after the advent of thermo-nuclear weapons testing (an is less than ~ 50 years old). Applicable calendar calibrations are included for materials between about 100 and 19,000 BP. If calibrations are not included with a report, those results were either too young, too old, or inappropriate for calibration. Please read the enclosed page discussing calibration.

4 Beta Analytic Inc SW 74 Court, Miami, Florida USA - Tel: Fax: beta@radiocarbon.com PRETREATMENT GLOSSARY Standard Pretreatment Protocols at Beta Analytic Unless otherwise requested by a submitter or discussed in a final date report, the following procedures apply to pretreatment of samples submitted for analysis. This glossary defines the pretreatment methods applied to each result listed on the date report form (e.g. you will see the designation acid/alkali/acid listed along with the result for a charcoal sample receiving such pretreatment). Pretreatment of submitted materials is required to eliminate secondary carbon components. These components, if not eliminated, could result in a radiocarbon date, which is too young or too old. Pretreatment does not ensure that the radiocarbon date will represent the time event of interest. This is determined by the sample integrity. Effects such as the old wood effect, burned intrusive roots, bioturbation, secondary deposition, secondary biogenic activity incorporating recent carbon (bacteria) and the analysis of multiple components of differing age are just some examples of potential problems. The pretreatment philosophy is to reduce the sample to a single component, where possible, to minimize the added subjectivity associated with these types of problems. If you suspect your sample requires special pretreatment considerations be sure to tell the laboratory prior to analysis. "acid/alkali/acid" The sample was first gently crushed/dispersed in deionized water. It was then given hot HCI acid washes to eliminate carbonates and alkali washes (NaOH) to remove secondary organic acids. The alkali washes were followed by a final acid rinse to neutralize the solution prior to drying. Chemical concentrations, temperatures, exposure times, and number of repetitions, were applied accordingly with the uniqueness of the sample. Each chemical solution was neutralized prior to application of the next. During these serial rinses, mechanical contaminants such as associated sediments and rootlets were eliminated. This type of pretreatment is considered a "full pretreatment". On occasion the report will list the pretreatment as "acid/alkali/acid - insolubles" to specify which fraction of the sample was analyzed. This is done on occasion with sediments (See "acid/alkali/acid - solubles" Typically applied to: charcoal, wood, some peats, some sediments, and textiles "acid/alkali/acid - solubles" On occasion the alkali soluble fraction will be analyzed. This is a special case where soil conditions imply That the soluble fraction will provide a more accurate date. It is also used on some occasions to verify the present/absence or degree of contamination present from secondary organic acids. The sample was first pretreated with acid to remove any carbonates and to weaken organic bonds. After the alkali washes (as discussed above) are used, the solution containing the alkali soluble fraction is isolated/filtered and combined with acid. The soluble fraction, which precipitates, is rinsed and dried prior to combustion. "acid/alkali/acid/cellulose extraction" Following full acid/alkali/acid pretreatments, the sample is bathed in (sodium chlorite) NaCIO 2 under very controlled conditions (Ph = 3, temperature = 70 degrees C). This eliminates all components except wood cellulose. It is useful for woods that are either very old or highly contaminated. Applied to: wood "acid washes" Surface area was increased as much a possible. Solid chunks were crushed, fibrous materials were shredded, and sediments were dispersed. Acid (HCI) was applied repeatedly to ensure the absence of carbonates. Chemical concentrations, temperatures, exposure times, and number of repetitions, were applied accordingly with the uniqueness of each sample. The sample was not be subjected to alkali washes to ensure the absence of secondary organic acids for intentional reasons. The most common reason is that the primary carbon is soluble in the alkali. Dating results reflect the total organic content of the analyzed material. Their accuracy depends on the researcher's ability to subjectively eliminate potential contaminants based on contextual facts. Typically applied to: organic sediments, some peats, small wood or charcoal, special cases

5 Beta Analytic Inc SW 74 Court, Miami, Florida USA - Tel: Fax: beta@radiocarbon.com PRETREATMENT GLOSSARY Standard Pretreatment Protocols at Beta Analytic (Continued) "collagen extraction: with alkali or collagen extraction: without alkali The material was first tested for friability ("softness"). Very soft bone material is an indication of the potential absence of the collagen fraction (basal bone protein acting as a "reinforcing agent" within the crystalline apatite structure). It was then washed in de-ionized water, the surface scraped free of the outer most layers and then gently crushed. Dilute, cold HCI acid was repeatedly applied and replenished until the mineral fraction (bone apatite) was eliminated. The collagen was then dissected and inspected for rootlets. Any rootlets present were also removed when replenishing the acid solutions. With alkali refers to additional pretreatment with sodium hydroxide (NaOH) to ensure the absence of secondary organic acids. Without alkali refers to the NaOH step being skipped due to poor preservation conditions, which could result in removal of all available organics if performed. Typically applied to: bones "acid etch" The calcareous material was first washed in de-ionized water, removing associated organic sediments and debris (where present). The material was then crushed/dispersed and repeatedly subjected to HCI etches to eliminate secondary carbonate components. In the case of thick shells, the surfaces were physically abraded prior to etching down to a hard, primary core remained. In the case of porous carbonate nodules and caliches, very long exposure times were applied to allow infiltration of the acid. Acid exposure times, concentrations, and number of repetitions, were applied accordingly with the uniqueness of the sample. Typically applied to: shells, caliches, and calcareous nodules "neutralized" Carbonates precipitated from ground water are usually submitted in an alkaline condition (ammonium Hydroxide or sodium hydroxide solution). Typically this solution is neutralized in the original sample container, using deionized water. If larger volume dilution was required, the precipitate and solution were transferred to a sealed separatory flask and rinsed to neutrality. Exposure to atmosphere was minimal. Typically applied to: Strontium carbonate, Barium carbonate (i.e. precipitated ground water samples) "carbonate precipitation" Dissolved carbon dioxide and carbonate species are precipitated from submitted water by complexing them as ammonium carbonate. Strontium chloride is added to the ammonium carbonate solution and strontium carbonate is precipitated for the analysis. The result is representative of the dissolved inorganic carbon within the water. Results are reported as "water DIC". Applied to: water "solvent extraction" The sample was subjected to a series of solvent baths typically consisting of benzene, toluene, hexane, pentane, and/or acetone. This is usually performed prior to acid/alkali/acid pretreatments. Applied to: textiles, prevalent or suspected cases of pitch/tar contamination, conserved materials. "none" No laboratory pretreatments were applied. Special requests and pre-laboratory pretreatment usually accounts for this.

6 Consistent Accuracy... Delivered On Time. Beta Analytic Inc SW 74 Court Miami, Florida USA Tel: Fax: Calendar Calibration at Beta Analytic Mr. Darden Hood Director Mr. Ronald Hatfield Mr. Christopher Patrick Deputy Directors Calibrations of radiocarbon age determinations are applied to convert BP results to calendar years. The short-term difference between the two is caused by fluctuations in the heliomagnetic modulation of the galactic cosmic radiation and, recently, large scale burning of fossil fuels and nuclear devices testing. Geomagnetic variations are the probable cause of longer-term differences. The parameters used for the corrections have been obtained through precise analyses of hundreds of samples taken from known-age tree rings of oak, sequoia, and fir up to about 10,000 BP. Calibration using tree-rings to about 12,000 BP is still being researched and provides somewhat less precise correlation. Beyond that, up to about 20,000 BP, correlation using a modeled curve determined from U/Th measurements on corals is used. This data is still highly subjective. Calibrations are provided up to about 19,000 years BP using the most recent calibration data available. The Pretoria Calibration Procedure (Radiocarbon, Vol 35, No.1, 1993, pg 317) program has been chosen for these calendar calibrations. It uses splines through the tree-ring data as calibration curves, which eliminates a large part of the statistical scatter of the actual data points. The spline calibration allows adjustment of the average curve by a quantified closeness-of-fit parameter to the measured data points. A single spline is used for the precise correlation data available back to 9900 BP for terrestrial samples and about 6900 BP for marine samples. Beyond that, splines are taken on the error limits of the correlation curve to account for the lack of precision in the data points. In describing our calibration curves, the solid bars represent one sigma statistics and the hollow bars represent two sigma statistics. Marine carbonate samples that have been corrected for 13 C/ 12 C, have also been corrected for both global and local geographic reservoir effects (as published in Radiocarbon, Volume 35, Number 1, 1993) prior to the calibration. Marine carbonates that have not been corrected for 13 C/ 12 C are adjusted by an assumed value of 0 %0 in addition to the reservoir corrections. Reservoir corrections for fresh water carbonates are usually unknown and are generally not accounted for in those calibrations. In the absence of measured 13 C/ 12 C ratios, a typical value of -5 %0 is assumed for freshwater carbonates. (Caveat: the correlation curve for organic materials assume that the material dated was living for exactly ten years (e.g. a collection of 10 individual tree rings taken from the outer portion of a tree that was cut down to produce the sample in the feature dated). For other materials, the maximum and minimum calibrated age ranges given by the computer program are uncertain. The possibility of an "old wood effect" must also be considered, as well as the potential inclusion of younger or older material in matrix samples. Since these factors are indeterminant error in most cases, these calendar calibration results should be used only for illustrative purposes. In the case of carbonates, reservoir correction is theoretical and the local variations are real, highly variable and dependent on provenience. Since imprecision in the correlation data beyond 10,000 years is high, calibrations in this range are likely to change in the future with refinement in the correlation curve. The age ranges and especially the intercept ages generated by the program must be considered as approximations.)

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8 FROM: Darden Hood, Director (This is a copy of the letter being mailed. Invoices/receipts follow only by mail.) March 17, 2004 Mr. Jack Meyer Sonoma State University Anthropological Studies Center 1801 East Cotati Avenue Building 29 Rohnert Park, CA USA RE: Radiocarbon Dating Results For Samples SF80-B1-1, SF80-B1-2, SF80-B1-3, SF80-B3-1, SF80-B3-2, SF80-B4-1, SF80-B4-2, SF80-B5-1, SF80-B6-1, SF80-B6-2, SF80-B6-3, SF80-B6-4, SF80-B6-5, SF80-B8-1, SF80-B8-2, SF80-B8-3, SF80-B10-1 Dear Jack: Enclosed are the radiocarbon dating results for 17 samples recently sent to us. They each provided plenty of carbon for accurate measurements and all the analyses went normally. As usual, the method of analysis is listed on the report with the results and calibration data is provided where applicable. As always, no students or intern researchers who would necessarily be distracted with other obligations and priorities were used in the analyses. We analyzed them with the combined attention of our entire professional staff. If you have specific questions about the analyses, please contact us. We are always available to answer your questions. Our invoice is enclosed. Please, forward it to the appropriate officer or send VISA charge authorization. Thank you. As always, if you have any questions or would like to discuss the results, don t hesitate to contact me. Sincerely,

9 Mr. Jack Meyer Report Date: 3/17/2004 Sonoma State University Material Received: 2/11/2004 Sample Data Measured 13C/12C Conventional Radiocarbon Age Ratio Radiocarbon Age(*) Beta /- 70 BP o/oo /- 70 BP SAMPLE : SF80-B1-1 ANALYSIS : Radiometric-Standard delivery (bulk low carbon analysis on sediment) MATERIAL/PRETREATMENT : (organic sediment): acid washes 2 SIGMA CALIBRATION : Cal BC 3010 to 2630 (Cal BP 4960 to 4580) Beta /- 60 BP o/oo /- 60 BP SAMPLE : SF80-B1-2 ANALYSIS : Radiometric-Standard delivery MATERIAL/PRETREATMENT : (peat): acid/alkali/acid 2 SIGMA CALIBRATION : Cal BC 3970 to 3700 (Cal BP 5920 to 5640) Beta /- 120 BP o/oo /- 120 BP SAMPLE : SF80-B1-3 ANALYSIS : Radiometric-Standard delivery (bulk low carbon analysis on sediment) MATERIAL/PRETREATMENT : (organic sediment): acid washes 2 SIGMA CALIBRATION : Cal BC 5200 to 5180 (Cal BP 7150 to 7130) AND Cal BC 5075 to 4525 (Cal BP 7025 to 6475) Beta /- 40 BP o/oo 150 +/- 40 BP SAMPLE : SF80-B3-1 ANALYSIS : AMS-Standard delivery MATERIAL/PRETREATMENT : (charred material): acid/alkali/acid 2 SIGMA CALIBRATION : Cal AD 1660 to 1950 (Cal BP 290 to 0) Beta /- 50 BP o/oo /- 50 BP SAMPLE : SF80-B3-2 ANALYSIS : AMS-Standard delivery MATERIAL/PRETREATMENT : (organic sediment): acid washes 2 SIGMA CALIBRATION : Cal BC 4460 to 4320 (Cal BP 6410 to 6270)

10 Mr. Jack Meyer Report Date: 3/17/2004 Sample Data Measured 13C/12C Conventional Radiocarbon Age Ratio Radiocarbon Age(*) Beta /- 40 BP o/oo 530 +/- 40 BP SAMPLE : SF80-B4-1 ANALYSIS : AMS-Standard delivery MATERIAL/PRETREATMENT : (organic sediment): acid washes 2 SIGMA CALIBRATION : Cal AD 1320 to 1350 (Cal BP 630 to 600) AND Cal AD 1390 to 1440 (Cal BP 560 to 510) Beta /- 40 BP o/oo 360 +/- 40 BP SAMPLE : SF80-B4-2 ANALYSIS : AMS-Standard delivery MATERIAL/PRETREATMENT : (peat): acid/alkali/acid 2 SIGMA CALIBRATION : Cal AD 1440 to 1640 (Cal BP 510 to 310) Beta /- 40 BP o/oo 520 +/- 40 BP SAMPLE : SF80-B5-1 ANALYSIS : AMS-Standard delivery MATERIAL/PRETREATMENT : (organic sediment): acid washes 2 SIGMA CALIBRATION : Cal AD 1320 to 1340 (Cal BP 630 to 600) AND Cal AD 1390 to 1440 (Cal BP 560 to 510) Beta /- 50 BP o/oo 240 +/- 50 BP SAMPLE : SF80-B6-1 ANALYSIS : Radiometric-Standard delivery (with extended counting) MATERIAL/PRETREATMENT : (peat): acid/alkali/acid 2 SIGMA CALIBRATION : Cal AD 1520 to 1590 (Cal BP 430 to 360) AND Cal AD 1620 to 1680 (Cal BP 330 to 260) Cal AD 1730 to 1810 (Cal BP 220 to 140) AND Cal AD 1930 to 1950 (Cal BP 20 to 0) Beta /- 60 BP o/oo 200 +/- 60 BP SAMPLE : SF80-B6-2 ANALYSIS : Radiometric-Standard delivery MATERIAL/PRETREATMENT : (peat): acid/alkali/acid 2 SIGMA CALIBRATION : Cal AD 1530 to 1560 (Cal BP 420 to 390) AND Cal AD 1630 to 1950 (Cal BP 320 to 0)

11 Mr. Jack Meyer Report Date: 3/17/2004 Sample Data Measured 13C/12C Conventional Radiocarbon Age Ratio Radiocarbon Age(*) Beta /- 50 BP o/oo 970 +/- 50 BP SAMPLE : SF80-B6-3 ANALYSIS : Radiometric-Standard delivery MATERIAL/PRETREATMENT : (organic sediment): acid washes 2 SIGMA CALIBRATION : Cal AD 990 to 1180 (Cal BP 960 to 760) Beta /- 40 BP +2.3 o/oo /- 40 BP SAMPLE : SF80-B6-4 ANALYSIS : AMS-Standard delivery MATERIAL/PRETREATMENT : (shell): acid etch 2 SIGMA CALIBRATION : Cal AD 220 to 440 (Cal BP 1730 to 1510) Beta /- 70 BP o/oo /- 70 BP SAMPLE : SF80-B6-5 ANALYSIS : Radiometric-Standard delivery MATERIAL/PRETREATMENT : (organic sediment): acid washes 2 SIGMA CALIBRATION : Cal BC 4810 to 4500 (Cal BP 6760 to 6450) Beta /- 60 BP o/oo 760 +/- 60 BP SAMPLE : SF80-B8-1 ANALYSIS : Radiometric-Standard delivery MATERIAL/PRETREATMENT : (organic sediment): acid washes 2 SIGMA CALIBRATION : Cal AD 1180 to 1300 (Cal BP 780 to 640) Beta /- 70 BP o/oo /- 70 BP SAMPLE : SF80-B8-2 ANALYSIS : Radiometric-Standard delivery (with extended counting) MATERIAL/PRETREATMENT : (peat): acid/alkali/acid 2 SIGMA CALIBRATION : Cal BC 810 to 400 (Cal BP 2760 to 2350)

12 Mr. Jack Meyer Report Date: 3/17/2004 Sample Data Measured 13C/12C Conventional Radiocarbon Age Ratio Radiocarbon Age(*) Beta /- 60 BP o/oo /- 60 BP SAMPLE : SF80-B8-3 ANALYSIS : Radiometric-Standard delivery (bulk low carbon analysis on sediment) MATERIAL/PRETREATMENT : (organic sediment): acid washes 2 SIGMA CALIBRATION : Cal BC 2460 to 2115 (Cal BP 4410 to 4065) AND Cal BC 2095 to 2040 (Cal BP 4045 to 3990) Beta /- 40 BP o/oo 840 +/- 40 BP SAMPLE : SF80-B10-1 ANALYSIS : AMS-Standard delivery MATERIAL/PRETREATMENT : (peat): acid/alkali/acid 2 SIGMA CALIBRATION : Cal AD 1060 to 1080 (Cal BP 890 to 860) AND Cal AD 1150 to 1270 (Cal BP 800 to 680)

13 (Variables: C13/C12=-26.5:lab. mult=1) 2 Sigma calibrated result: Beta ±70 BP Cal BC 3010 to 2630 (Cal BP 4960 to 4580) Intercept of radiocarbon age with calibration curve: Cal BC 2885 (Cal BP 4835) 1 Sigma calibrated results: Cal BC 2910 to 2865 (Cal BP 4860 to 4815) and Cal BC 2795 to 2770 (Cal BP 4745 to 4720) ±70 BP Organic sediment Ca l BC

14 (Variables: C13/C12=-22.7:lab. mult=1) 2 Sigma calibrated result: Intercepts of radiocarbon age with calibration curve: 1 Sigma calibrated result: Beta ±60 BP Cal BC 3970 to 3700 (Cal BP 5920 to 5640) Cal BC 3910 (Cal BP 5860) and Cal BC 3880 (Cal BP 5830) and Cal BC 3800 (Cal BP 5750) Cal BC 3950 to 3770 (Cal BP 5900 to 5720) ±60 BP Peat Ca l BC

15 (Variables: C13/C12=-25.3:lab. mult=1) 2 Sigma calibrated results: Beta ±120 BP Cal BC 5200 to 5180 (Cal BP 7150 to 7130) and Cal BC 5075 to 4525 (Cal BP 7025 to 6475) Intercept of radiocarbon age with calibration curve: Cal BC 4800 (Cal BP 6750) 1 Sigma calibrated result: Cal BC 4945 to 4700 (Cal BP 6895 to 6650) ±120 BP Organic sediment Ca l BC

16 (Variables: C13/C12=-25.6:lab. mult=1) 2 Sigma calibrated result: Intercepts of radiocarbon age with calibration curve: 1 Sigma calibrated results: Beta ±40 BP Cal AD 1660 to 1950 (Cal BP 290 to 0) Cal AD 1680 (Cal BP 270) and Cal AD 1740 (Cal BP 210) and Cal AD 1810 (Cal BP 140) and Cal AD 1930 (Cal BP 20) and Cal AD 1950 (Cal BP 0) Cal AD 1670 to 1700 (Cal BP 280 to 250) and Cal AD 1720 to 1780 (Cal BP 230 to 170) and Cal AD 1800 to 1820 (Cal BP 150 to 130) and Cal AD 1840 to 1880 (Cal BP 110 to 70) and Cal AD 1920 to 1950 (Cal BP 30 to 0) ±40 BP Charred material Cal AD

17 (Variables: C13/C12=-25.2:lab. mult=1) 2 Sigma calibrated result: Beta ±50 BP Cal BC 4460 to 4320 (Cal BP 6410 to 6270) Intercept of radiocarbon age with calibration curve: Cal BC 4350 (Cal BP 6300) 1 Sigma calibrated result: Cal BC 4380 to 4340 (Cal BP 6330 to 6290) ±50 BP Organic sediment Ca l BC

18 (Variables: C13/C12=-25.9:lab. mult=1) 2 Sigma calibrated results: Beta ±40 BP Cal AD 1320 to 1350 (Cal BP 630 to 600) and Cal AD 1390 to 1440 (Cal BP 560 to 510) Intercept of radiocarbon age with calibration curve: Cal AD 1420 (Cal BP 540) 1 Sigma calibrated result: Cal AD 1400 to 1430 (Cal BP 550 to 520) ±40 BP Organic sediment Cal AD

19 (Variables: C13/C12=-26.4:lab. mult=1) 2 Sigma calibrated result: Beta ±40 BP Cal AD 1440 to 1640 (Cal BP 510 to 310) Intercept of radiocarbon age with calibration curve: Cal AD 1500 (Cal BP 450) 1 Sigma calibrated results: Cal AD 1460 to 1530 (Cal BP 490 to 420) and Cal AD 1560 to 1630 (Cal BP 390 to 320) ±40 BP Peat Cal AD

20 (Variables: C13/C12=-25.9:lab. mult=1) 2 Sigma calibrated results: Beta ±40 BP Cal AD 1320 to 1340 (Cal BP 630 to 600) and Cal AD 1390 to 1440 (Cal BP 560 to 510) Intercept of radiocarbon age with calibration curve: Cal AD 1420 (Cal BP 530) 1 Sigma calibrated result: Cal AD 1410 to 1430 (Cal BP 540 to 520) ±40 BP Organic sediment Cal AD

21 (Variables: C13/C12=-26:lab. mult=1) 2 Sigma calibrated results: Beta ±50 BP Cal AD 1520 to 1590 (Cal BP 430 to 360) and Cal AD 1620 to 1680 (Cal BP 330 to 260) and Cal AD 1730 to 1810 (Cal BP 220 to 140) and Cal AD 1930 to 1950 (Cal BP 20 to 0) Intercept of radiocarbon age with calibration curve: Cal AD 1660 (Cal BP 290) 1 Sigma calibrated results: Cal AD 1640 to 1670 (Cal BP 310 to 280) and Cal AD 1780 to 1800 (Cal BP 170 to 150) ±50 BP Peat Cal AD

22 (Variables: C13/C12=-26.4:lab. mult=1) Beta Sigma calibrated results: 200±60 BP Cal AD 1530 to 1560 (Cal BP 420 to 390) and Cal AD 1630 to 1950 (Cal BP 320 to 0) Intercept of radiocarbon age with calibration curve: Cal AD 1670 (Cal BP 280) 1 Sigma calibrated results: Cal AD 1650 to 1680 (Cal BP 300 to 260) and Cal AD 1730 to 1810 (Cal BP 220 to 140) and Cal AD 1930 to 1950 (Cal BP 20 to 0) ±60 BP Peat Cal AD

23 (Variables: C13/C12=-28.9:lab. mult=1) 2 Sigma calibrated result: Beta ±50 BP Cal AD 990 to 1180 (Cal BP 960 to 760) Intercept of radiocarbon age with calibration curve: Cal AD 1030 (Cal BP 920) 1 Sigma calibrated results: Cal AD 1010 to 1060 (Cal BP 940 to 890) and Cal AD 1080 to 1150 (Cal BP 860 to 800) ±50 BP Organic sediment Ca l AD

24 (Variables: C13/C12=2.3:Delta-R=225±35:Glob res=-200 to 500:lab. mult=1) Beta ±40 BP (2050±50 adjusted for local reservoir correction) 2 Sigma calibrated result: Cal AD 220 to 440 (Cal BP 1730 to 1510) Intercept of radiocarbon age with calibration curve: Cal AD 340 (Cal BP 1610) 1 Sigma calibrated result: Cal AD 260 to 400 (Cal BP 1690 to 1540) ±40 BP (2050±50 adjusted) Shell Ca l AD Marine98

25 (Variables: C13/C12=-24.1:lab. mult=1) 2 Sigma calibrated result: Beta ±70 BP Cal BC 4810 to 4500 (Cal BP 6760 to 6450) Intercept of radiocarbon age with calibration curve: Cal BC 4700 (Cal BP 6650) 1 Sigma calibrated result: Cal BC 4740 to 4580 (Cal BP 6690 to 6530) ±70 BP Organic sediment Ca l BC

26 (Variables: C13/C12=-26.1:lab. mult=1) 2 Sigma calibrated result: Beta ±60 BP Cal AD 1180 to 1300 (Cal BP 780 to 640) Intercept of radiocarbon age with calibration curve: Cal AD 1270 (Cal BP 680) 1 Sigma calibrated result: Cal AD 1230 to 1290 (Cal BP 720 to 660) ±60 BP Organic sediment Cal AD

27 (Variables: C13/C12=-22.2:lab. mult=1) 2 Sigma calibrated result: Intercepts of radiocarbon age with calibration curve: 1 Sigma calibrated results: Beta ±70 BP Cal BC 810 to 400 (Cal BP 2760 to 2350) Cal BC 760 (Cal BP 2710) and Cal BC 620 (Cal BP 2560) and Cal BC 590 (Cal BP 2540) Cal BC 790 to 500 (Cal BP 2740 to 2450) and Cal BC 460 to 430 (Cal BP 2410 to 2380) ±70 BP Peat Ca l BC

28 (Variables: C13/C12=-25.2:lab. mult=1) 2 Sigma calibrated results: Intercepts of radiocarbon age with calibration curve: 1 Sigma calibrated result: Beta ±60 BP Cal BC 2460 to 2115 (Cal BP 4410 to 4065) and Cal BC 2095 to 2040 (Cal BP 4045 to 3990) Cal BC 2265 (Cal BP 4215) and Cal BC 2260 (Cal BP 4210) and Cal BC 2220 (Cal BP 4170) Cal BC 2330 to 2145 (Cal BP 4280 to 4095) ±60 BP Organic sediment Ca l BC

29 (Variables: C13/C12=-26:lab. mult=1) 2 Sigma calibrated results: Beta ±40 BP Cal AD 1060 to 1080 (Cal BP 890 to 860) and Cal AD 1150 to 1270 (Cal BP 800 to 680) Intercept of radiocarbon age with calibration curve: Cal AD 1210 (Cal BP 740) 1 Sigma calibrated result: Cal AD 1180 to 1250 (Cal BP 780 to 700) ±40 BP Peat Cal AD

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